Absorbent articles such as sanitary napkins, pantiliners, disposable diapers, incontinent briefs, and bandages are designed to absorb and retain liquid and other discharges from the human body and to prevent body and clothing soiling. Typically, most disposable absorbent articles are made of materials that will not readily stretch under the forces that the absorbent article is normally subjected to when worn. The inability of the materials comprising the absorbent article to stretch when subjected to normal wearing forces causes the absorbent article to have certain drawbacks. One drawback is the lack of comfort for the wearer. The wearer should ideally be able to notice a difference between an absorbent article that stretches to conform to the wearer's body with the wearer'movements and an absorbent article that fails to stretch. For example, a conventional prior art sanitary napkin does not move with the wearer's undergarments, thereby causing the sanitary napkin to shift which may cause a degree of discomfort for the wearer. Enabling all or a portion of a sanitary napkin to stretch under normal wearing conditions and forces will permit the sanitary napkin to better conform to the wearer's undergarment and stay in place even when the wearer moves.
Several attempts have been made to make one or more components of absorbent articles stretchable in response to relatively low wearing forces. Typical prior art solutions rely on the addition of traditional elastics such as natural or synthetic rubber. For example, traditional elastics have been secured to portions of the topsheet and/or backsheet of absorbent articles, such as the waist portion of a disposable diaper, to provide a better fit and overall comfort for the wearer. However, traditional elastics are costly and require a certain degree of manipulation and handling during assembly. While traditional elastics do provide a degree of stretch for the absorbent article, the materials to which the traditional elastic is secured are typically not normally considered elastic or stretchable. Therefore, the added traditional elastics must be prestretched prior to being secured to the material or the material must be subjected to mechanical processing, e.g., ring rolling to permanently elongate the material to extend beyond its initial untensioned length and allow the added traditional elastic to be effective. Otherwise, the added traditional elastic is restrained by the material and is rendered inoperable. An example of an absorbent article having a web material which has been subjected to additional processing to allow the web material to more easily extend with the added traditional elastic member is disclosed in U.S. Pat. No. 5,151,092 issued to Buell et al. on Sep. 29, 1992 and hereby incorporated herein by reference. The Buell patent describes an operation which prestrains a backsheet so that the backsheet will, upon mechanical stretching, be permanently elongated and not fully return to its original undistorted configuration. Buell teaches that a traditional elastic member must be added to the prestrained backsheet material for the invention to be operable. Buell also discloses that a prestrained backsheet improves the extension and the heat-shrink contraction of the added traditional elastic member.
Accordingly, it is an object of the present invention to provide web materials which exhibit an "elastic-like" behavior in the direction of applied elongation without the use of added traditional elastic. As used herein, the term "elastic-like" describes the behavior of web materials which when subjected to an applied elongation, the web materials extend in the direction of applied elongation and when the applied elongation is released the web materials return, to a substantial degree, to their untensioned condition. While such web materials exhibiting an elastic-like behavior have a wide range of utility, e.g. durable articles of apparel, disposable articles of apparel, covering materials such as upholstery, wrapping materials for complex shapes and the like, they are particularly well suited for use as a topsheet, a backsheet, and/or an absorbent core in an absorbent article.